Condensed Consolidated Statement of Other Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011
Statement of Other Comprehensive Income [Abstract]
Document Period End Date			Oct. 31, 2012
Net income	$ 29.4	$ 72.8	$ 172.9	$ 213.3
Other comprehensive income, net of tax and reclassification [Abstract]
Net loss on derivative instruments	(12.1)	(3.3)	(8.6)	(2.8)
Change in net unrealized gain on available-for-sale securities	(1.2)	(1.4)	(0.8)	(0.4)
Net change in cumulative foreign currency translation gain	6.3	(6.2)	(2.9)	7.2
Total other comprehensive (loss) income	(7.0)	(10.9)	(12.3)	4.0
Total comprehensive income	$ 22.4	$ 61.9	$ 160.6	$ 217.3